Decorative shell



FIG. 1 is an isometric view of the decorative shell;

FIG. 2 is a first side elevational view thereof;

FIG. 3 is a second side elevational view thereof;

FIG. 4 is a third side elevational view thereof;

FIG. 5 is a fourth side elevational view thereof; and,

FIG. 6 is a plan view thereof.

Structures shown in phantom form no part of the claimed design. 

The ornamental design for a decorative shell, as shown and described. 